SAN FRANCISCO—System builders may spend more time thinking about PCI Express (PCIe) than any other brand of consumer, but even they probably give it passing thought only when it comes to video cards. But at the Intel Developer Forum here, the PCI Special Interest Group (PCI-SIG) is reminding people that, like so much else with computers, it's a constantly evolving technology, and one that will find its next permanent form by the end of the year.

The current focus of the group, which was founded in 1992 to develop and manage the PCI standard, is PCIe 3.0. This latest incarnation of the specification builds on PCIe 2.0 (released in 2007), by offering improved data rates (8 gigatransfers per second as opposed to 5) and encoding (128- and 130-bit versus 8- and 10-bit when operating at 8 GTps), the latter of which the PCI-SIG allows 98.5 percent efficiency. PCIe 3.0 will also be backwards compatible with both PCIe 1 and PCIe 2 specs.

Architecture

Raw Bit Rate

Interconnect Bandwidth

Bandwidth per Lane per Direction

Total Bandwidth for x16 Link

PCIe 1.x

2.5 GTps

2 Gbps

~250 MBps

~8 GBps

PCIe 2.x

5 GTps

4 Gbps

~500 MBps

16 GBps

PCIe 3.0

8 GTps

8 Gbps

~1 GBps

~32 GBps

Also among the new features in the PCIe 3.0 architecture is Dynamic Feedback Equalization (DFE). This is a technique in electrical signaling that adapts to the time-vairant properties of the transmission medium to obtain an optimum Signal-to-Noise ration at the sample point of the receiver. Representatives of the PCI-SIG say that DFE will improve the PCIe bus signal integrity.

The development of PCIe 3.0 is expected to facilitate the development of faster Ethernet technology, InfiniBand, PCIe switches, and high-capacity storage (especially solid-state drives).

According to PCI-SIG President and Chairman Al Yanes, the PCIe 3.0 specification is expected to be published in November, following a 60-day IP review on the heels of the release of the most recent version, PCIe 3.0 Rev 0.9, on August 16. (It may be read on the PCI-SIG Web site.)

Consumer products, such as motherboards, using PCIe 3.0 may be seen as early as the second half of next year.

Matthew Murray got his humble start leading a technology-sensitive life in elementary school, where he struggled to satisfy his ravenous hunger for computers, computer games, and writing book reports in Integer BASIC. He earned his B.A. in Dramatic Writing at Western Washington University, where he also minored in Web design and German. He has been building computers for himself and others for more than 20 years, and he spent several years working in IT and helpdesk capacities before escaping into the far more exciting world...
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